This application seeks to acquire a fluorescence-activated cell sorter to be shared by several research groups or units at this Medical Center. There is currently no such facility at this Center. The nearest one, at the Naval Blood Research Laboratories, tends to have its time fully committed to the NBRL's own research endeavors; while it has been possible for some of the applicants to have cells put through occasionally there - or at the less easily reached FACS at MIT - it has not been possible to do so frequently in virtually all cases, nor has it been possible to plan a full research project which depends upon assured, planned, frequent access to a FACS. We are hence seeking our own, to be supervised by Dr. Simons, housed on the Cancer Center's floor, and operated by a trained full time operator. The research to be performed on this instrument spans many fields. immunology, hematology, cell biology being the salient ones. We plan to use the facility to sort and identify: (a) subpopulations of lymphocytes having specific properties, e.g. capability of modulationg granulopoeisis; (b) malignnat subpopulations of B lymphocytes against whose surface immunoglobulins: "anti-idiotypic" antibodies will be produced; (c) study the T lymphocytes from severe trauma patients in order to investigate the severe immunoincompetence which sometimes accompanies trauma (d) study the role of the two classes of thrombin receptors on platelets and the mechanism by which they regulate platelet clot formation initially, and resorption eventually (e) investigate the potentiation of stimulus response of a secretory cell (platelet or neotrophil) upon preexposure to suboptimal doses of stimuli (f) investigate the effect of age on the immune response by focusing on its role in controlling or modulating the population and/or the functional characteristics of lymphocytes (g) study the control and the production of macrophage-derived growth factor by various classes of human monocytes. All of the above investigations are either planned by or are already part of the ongoing research plans of investigators at the Boston University Medical Center, but cannot be performed without a fluorescence-activated cell sorter system. Such a system is not currently in existence, nor is there assured access by the applicants to any other facility in this area.